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Assignment Failure(revision to old chan)

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  • #63288 Reply
    bipin jaiswal
    Guest

    I faced that issue on BCCH-Trx.most of the time ms send Assignment failure(Revision to old channel). In Tems log MS retries SABME frame,butTRX does not recieve it.can anyone please tell me the reason for that issue?

    #63289 Reply
    Mania
    Guest

    Hi,
    Are you talking about the Call Setup or the Handover phase..
    Normally ROC is pegged when the destination TS cannot be successfully camped on and reverts. In Call setup if its assigned to inner zone and a feature like second assignment is there then too its pegged check the assignment / handover command for the TRX to which the call is assigned at. Its HW can be faulty / check its frequency, if SFN check MAL /MAIO if fixed frequency check the C/I plot of the frequencies to identify the problematic frequency. or disable hopping (and swap frequencies assigned to TRX) to check which frequency / HW is generating the Reversions

    #63290 Reply
    bipin
    Guest

    Thanks mania for your response. I faced that issue on BCCH-TRX in call setup scenario. Hopping is off on TRX. I had increase the bcch-tx-pwr 30dbm to 40 dbm,after that this issue was resolve. but still I do not find the reason for that issue.

    #63291 Reply
    bipin
    Guest

    I am still facing the same issue.
    can anyone please help me to resolve that issue?

    #63292 Reply
    pix
    Guest

    hi bipin,

    perhaps you should describe your probleml better

    is it a dualband cell (concentric) ?
    which vendor is it ?
    during call setup, how can a MS be reverted to the old channel ? There is no old channel !

    Changing the BCCH TX POWER is weird… is there such a parameter ? Normally all TRXs are emitting at the same power, except in specific implementation of concentric cells.

    cheers
    pix

    #63293 Reply
    Rex
    Guest

    Hi bipin,
    Are you sure you get assignment failure (ROC) from the same cell where the call was initiated? If Yes, I’m gonna ask maybe stupid question. Is that maybe related somehow to Forced Directed Retry? SDCCH(Cell A)-TCH(Cell B) phase, TCH on Cell B is busy, go back to Cell A?! Just assumption.
    Regards,
    Rex.

    #63294 Reply
    bipin
    Guest

    I am working on D-TRX(dual trx) board which is configured as bcch(TS0-bcch, TS1-sdcch/8,TS2-7-tch) and non-bcch(all tch channels)trx.
    some time call is fail on non-bcch trx due to revision to old channel.if i analyze the Tems logs,in that log ms recieve the assignment command message and ms start sending sabm frame to trx. but trx did no recive it. after max. no of retry(n200), ms resume the sddch-ladm link and send assignmet failure(roc). most of the time i faced that issue on non-bcch trx. some time that scenario is happen on bcch-trx. i had doubt about frame sync between both trx.as per my understanding frame number on both trx should be same.

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